SAN DIEGO (CNS) - A fire that tore through a docked commercial fishing and research ship Friday near Seaport Village will likely continue to burn into Saturday night.

The blaze erupted for unknown reasons inside the 120-foot Norton Sound at about 9:30 a.m. Friday.

It was unclear if anyone was aboard the vessel when the fire broke out. Firefighters initially battled the flames from inside, finding no victims, but were ordered to pull out because of the intensity of the fire inside the boat after about a half-hour.

The fire seemed to mostly burn itself out, then flared up again later in the day Friday. Firefighters stayed on scene all night to monitor the ship, rotating every three hours, according to San Diego Fire-Rescue Department spokesperson Monica Munoz.

Crews also checked the mooring lines every hour to ensure they did not burn, Munoz said.

The fire appeared to be localized in the bow of the vessel on Saturday, she said.

Munoz said firefighters will continue to apply water to the outside of the hull to cool the vessel. Crews cannot enter the vessel until temperatures drop to a safe level. Thermal imaging showed temperatures of over 300 degrees Fahrenheit inside the vessel, Munoz said.

Firefighters do not have an estimate on when the blaze will be put out, Munoz said. Two engine companies were at the scene Saturday afternoon, but this will be scaled back to one engine company at 8 p.m., she said. That engine company will continue to monitor the fire throughout the night.

One firefighter was taken to a hospital for treatment of heat exhaustion after battling the blaze late Friday morning, and was released about 5 p.m. the same day, Munoz said.